Magnetic and magnetocaloric properties of R₅₅Co₃₀Al₁₀Si₅ (R = Ho, Dy) metallic glass ribbons

Metallic glass alloys are suitable systems for the development of magnetocaloric refrigerated materials due to the stable physical properties and the adjustable magnetic phase transition temperature. Here, the glass formation ability (GFA), magnetic properties and magnetocaloric effects of R₅₅Co₃₀Al₁₀Si₅ (R = Ho, Dy) amorphous ribbons prepared by the melt-spinning technique were investigated. The X-ray diffraction and DSC measurement indicated that the metallic glass alloys have a completely amorphous structure and excellent glass formation ability. The amorphous ribbons were demonstrated to undergo a second-order magnetic phase transition (ferromagnetic to paramagnetic) around T_c ∼ 18 K for Ho₅₅Co₃₀Al₁₀Si₅, ∼34 K for Dy₅₅Co₃₀Al₁₀Si₅, respectively. The maximum magnetic entropy change (-ΔS_M^max) and the corresponding refrigerant capacity (RC) values are 12.7 J/kg K, 343 J/kg for Ho₅₅Co₃₀Al₁₀Si₅, 9.1 J/kg K, 334 J/kg for Dy₅₅Co₃₀Al₁₀Si₅ under a field change ΔH= 5 T. The large -ΔS_M^max and high RC suggest that R₅₅Co₃₀Al₁₀Si₅ (R = Ho, Dy) amorphous ribbons have potential applications in low temperature magnetic refrigeration.